Wireless signaling system



A. N. GOLDSIV'IIIII.

WIRELESS SIGNALING SYSTEM.

APPLICATION FILED IAN. IB. I9I1.

Fig. I

/4 lill/? Patented Deo. y,2, 1919.

Paqui/fil) Alfred. N. Goldsmith,

bsd/MMM sTATEs PATENT onnicn.

ALFRED N. GOLDSMITH, OF NEW YORK, N. Y., ASSIG'N OR TO GENERAL ELECTRIC i COMPANY, A CORPORATION OF NEW YORK.

WIRELESS SIGNALIN SYSTEM.

. Specification of Letters Patent.

' Patented Dec. 2, 1919.

Application led January 18, 1317'. Serial No. 143,035.

New York, have invented certain new and useful Improvements in Wireless Signaling Systems, of which the following is a specification.

My present invention relates to the eilicientl production of radio frequency continuous electrical oscillations in a radiating system, and to means for c-ontrollin amplitude of such oscillations in accor ance with the variations in the amplitude of a controlling current which may be produced by sound waves.

It has been found that an electron discharge device comprising an incandescent cathode, a cooperating anode, and a discharge controlling member or grid inclosed in an evacuated envelop may be employed for producing radio frequency oscillations. In order to secure this result a source of -energy -is* placed lin the plate circuit of the device, which includes the cathode, the anode, and an inductance, and this circuit is coupled with the grid circuit, which in chicles the cathode and grid, and a second inductance. If a suitable degree of coupling is provided between the two circuits enough energy is transferred from the plate circuit to the grid circuit to impress upon the grid the potential necessary to control the flow of current in the plate circuit in the desired manner. In some cases the electrostatic coupling between the two circuits, which is always present by reasony of the capacity between the electrodes, is sufficient to bring about the desired result. In other cases this is supplemented in various ways, as, for exam-ple, by a coupling between the inductances in the two circuits, or by an additional electrostatic coupling consisting of a condenser between the grid and anode, or by a combination of the two forms of coupling. Because of the unidirectional conductivity of the electron discharge device, the currentin the plate circuit will usually be pulsating in character. For practical purposes, however, it may be considered 'asy being made up of two components, one a constant direct current, and the second an alternating current superimposed upon the direct current. In order to utilize this the l alternating component in a radiating system it has been customary to couple a coil in the antenna'with the plate circuit indue-- tance. It has also been customary to employ variable condensers in the plate or grid circuits, or in -both circuits, for tuning the system to produce the desired frequency of oscillations. With the system heretofore employed in order to secure maximum efflciency of output, it has also been necessary that the antenna should be tuned to the same frequency as the system which produces the oscillations. 1

One of the objects of my invention is to provide a system in which the entire tuning may be accomplished by varying one .of the constants 'of the antenna, and in whichthe necessity o-f an inductive coupling between the antenna and the system produc-ing oscillations is avoided. In accomplishing this object I include 'the grid and plate circuit inductances directly in the antenna, and the capacity of the' antenna is made use of in place of the condensers previously employed for tuning the grid or plate circuits.

In case it is desired to utilize the radio frequency oscillations produced by the electron discharge device for the transmission of sound waves, it has been proposed to superimpose upon the grid circuit of the device a variable current produced by means of the sound waves which .it is desired to grec of control which can be secured is limited to some extent by the amount of energyI which can be controlled by an ordinary telephone transmitter. Hence it will be apparent that if means isprovided for amplifying the current variations produced by the telephone transmitter a larger degree of control may be secured. A further object of my invention is to provide simple and efficient means for amplifying the audio frequency current produced by vthe telephone transmitter. In accomplishing this object I provide an audio frequency coupling be- .transmit With this arrangement the de-v tween the grid and. plate circuits. When the telephone current is'superimposed upon the grid circuit corresponding but amplified variations are produced in the current in the plate circuit. These amplified current Variations are, by means of the audio frequency coupling fed back into the grid circuit, and as a result the audio frequency potential variations -upon the grid are made much greater than it is possible to secure by means of the original telephone current alone.

The features of my invention which I consider novel are 'pointed out with particularity in lthe appended claims. The invention itself, however, bothas to its organization and method of operation will best be understood by' reference to the following description taken in connection with the accompanying drawing, in which Figure 1 shows diagrammatically one embodiment of my invention, Fig.. 1A shows a portion of the circuit of Fig. 1 slightly modified, and Fig.

2 shows a modification in which the possible e output is increased by the use of a plurality of electron discharge devices in parallel for producing oscillations.

As indicated in the drawing, an electron discharge device is used which comprises an electron emitting cathode 1 of filamentary form, a plate-shaped anode 2, and a grid 3 interposed between the cathode and the anode, all inclosed in an evacuated envelop .4. The plate circuit of this device includes the cathode 1, anode 2, an'inductance 5, and a source of energy 6, which may be a direct current generator, as indicated, or any other convenient source of direct current. Current for heating the cathode 1 to cause it to emit electrons is supplied by a battery 7, or any other convenient source of current, the means for regulating the heating current which is customarily used being omitted in order to simplify the drawing. The grid circuit comprises the cathode 1, grid 3, an inductance v8 and coils 9 and 10 of transformers adapted to the transformation of audio frequency currents, for eX- ample, the iron core transformers 11 and 12. I may also include a battery 13 for the purpose of giving the grid a normal potentiall at which the device operates most ,eliiciently The antenna 14 ymay be connected to the top of inductance 8 through a tuning coil 15, or directly connected to the top of coil 8, depending upon the antenna ycharacteristics, as hereinafter explained,

and the radiating system is grounded art 16 through inductances 8 and 5. With the connection thus far described the grid and plate circuits are coupled electrostatically by,

reason of the capacity between the electrodes 1, 2 and 3, and this coupling is supplemented by the capacity of the antenna whichis in effect connected between the grid 3 and anode 2. The relative positions of coils 'aud may also be made such as to furnish any desired degree .of inductive coupling between the two circuits.

It isdesirable to have the effective impedance in the output circuit of an oscillating discharge device, or several such devices in parallel or series, equivalent to the net internal impedance, which is mostly retion.

' a similar means of adjustment though in the opposite sense.

The arrangement thus described is adapted to produce radio frequency continuous oscillations, the frequency of which may be varied by varying the tuning of the system by means of the tuning coil 15. The tuning of the system may also be varied by varying the inductance of coil 8 or coil 5, or, if desired, a variable condenser 15a may be connected between the bottom of coil 5 and ground as shown in Fig. 1A. It will also be apparent that the desired result may be obtained by varying any two or more of the above-mentioned elements. In order to control the amplitude of the oscillations thus produced in accordance with the lamplitude of the current produced by sound waves, current from the telephone transmitter 17 supplied by a local battery 18 is caused to flow through the primary 19 of the transformer 11. When the transmitter 17 is acted upon by sound waves, a variable telephone current will flow through the rimary 19 of the transformer 11. The potential of the grid 3 is thus caused to vary in accordance with variations in the telephone current and the amplitude of the oscillations produced in the antenna will thereby be varied in accordance with the variations in the current through the transmitter. The current in the plate circuit will vary in the same way. This current will now have in addition to the radio freqency component an audio frequency com` ponent whichvaries in accordance with the variations in the telephone current, and this component is caused to flow through the primary 20 of transformer 12, and is thus superimposed upon the grid circuit causing a further increase in the amplitude of the audio frequency potential variations upon the grid, provided the coils 19, 9, 20 and 10, are connected in such a way as to give the proper polarity to secure the reinforcing action. Condenser 21 in the plate circuit which shunts the primary 20 is given such a value that it offers a low impedance to the radio frequencyn component of the plate circuit but a high impedance to the audio frequency component. The condenser 22 which shunts secondaries 9 and 10 of transformers 11 and 12 is also given such a value that it offers a low impedance path to the radio frequency component of the current inthe grid circuit. Condenser 23 may be employed for shunting the source of current 6 in order that the radio frequency component of current in the plate circuit will not be compelled to pass through this source- In the arrangement shown in Fig. 2 a plurality of electron discharge devices connected in parallel are employed for producing oscillations, the cathodes of all of these devices being supplied with heating current by the common battery 24 or other suitable source. In this case the source of current G instead of being connected in series in the plate circuit is connected in a parallel branch, and the inductance 25 is employed to prevent the radio frequency component of the plate current from flowing through source 6 and to insure ehicient production of radio frequency energy. The coil 25 acts as a. maintaining inductance in that it gives rise to radio frequency potential differences at its terminals. The result is that the plate circuit voltage of the electron discharge device, that is, the voltage between filament and plate, is variable with a radio frequency con'lpo'nent. Because of the phase of the grid potential control, the voltage is highest when the internal resistance in the bulb is highest between plate and filament, and the external volta-ge is least when the internal resistance is least. Therefore, less energy is absorbed per cycle in the discharge device, and increased efficiency results. Condenser 26 iny the second branch of the plate circuit serves to prevent the direct current component of the plate current from {iowingthrough this branch. In this case separate condensers 27 and 28 are employed for shunting the coils 9 and 10 instead of the single condenser 22 employed in the arrangement shown in Fig. 1. In this form of my invention, the grid circuit consists of two portions. The first portion is the inductance 30, which substantially prevents the passage of alternating current through .this portion, and the battery 31 which replaces in' function the battery 13, Fig. 1, for giving the grid a normal potential at which the device operates most efliciently. The second portion consists, as in Fig'. 1, of the coil 8, coils 9 and 10 shunted by their respective condensers 28 and 27, and the condenser 29 which readily passes all alternating current but prevents the passage of current from battery 31 through the second portion.

VVhileI have shown only two modifications of my invention, I do not wish to be limited to the exact circuit arrangement shown as it will be apparent that many modifications in the arrangement yof the apparatus, aswell as in the particular type of apparatus used, may be made without departing from the scope of my invention. as set It will also be apparent that the oscillating system which I have described may be employed for transmitting either telephonic or telegraphic signals over a transmission line.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination in a Wireless signaling system of an anterma, and an electron discharge device having grid and plate cir- .cuits containing inductances, said antenna being connected to earth through said inductances, and said grid and plate circuits being so coupled together that radio frequency oscillations will be produced in said antenna.

2. The combination in a wireless signaling system of an antenna, an electron discharge device having grid and plate circuits contalnmg lnductances, connections between the antenna andA earth through said inductances, said grid and plate circuits being so coupled together that'radio frequency oscillations will be produced in said antenna, and means in said antenna circuit for tuning the same, thereby varying the frequency of the oscillations produced.

3. The combination in a wireless signaling system of an electron discharge device having grid and plate circuits so organized and coupled together that radio frequency oscillations will be 4produced therein, means for impressing an audio frequency current upon the grid circuit and thereby varying the amplitude of the oscillations produced at an audio frequency, a condenser in the plate circuit of the device which offers a low impedance to the radio frequency component of the vcurrent flowing therein, and

a high `impedance to the audio frequency componentof the current in the plate circuit, a coil shunting said condenser through which the audio frequency component of the current in the plate circuit will flow, said coil formingthe primary of an audio freis included in series in the grid circuit.

4. The combination in a wireless signaling system of an electron discharge device having grid and plate circuits containing inductances, said grid and plate circuits being so coupledltogether that radio frequency oscillations will be produced therein, means for impressing an audio frequency current upon the grid circuit for varying the amplitude of the oscillations producedlat an audiquency transformer, the secondary of which ble frequency, and a coupling between said plate and grid circuits adapted to transfer energy from the plate circuit to the grid circuit, at an audible frequency without transferring an appreciable amount of radio frequency energy from the plate to the grid circuit.

5. The combination in a wireless signaling system of an'antenna, an electron discharge device having grid and plate circuits containing inductances, connections between the antenna and earth through said inductances, said grid and plate circuits being so coupled'together that radio frequency .oscillations will be produced in said antenna, means for impressing an audio frequency current upon said grid circuit for varying the amplitude of the oscillations produced in said antenna at an audible frequency and a coupling between the plate and grid cir-v cuits for transferring energy at the audio frequency from the plate to the grid circuit and thereby amplifying the effect in the grid circuit of the audio frequency current therein. y

The combination in a system for transmitting signals of an electron discharge device having grid and plate circuits so coupled together that radio frequency currents will be produced therein, means for impressing a low frequency signaling current on the grid circuit and a coupling between the two circuits which is adapted to transfer energy at an audio frequency from the plate circuit to the grid circuit without transferring an appreciable amount of radio frequency energy.

i. The combination in a system for transmitting signals of an electron discharge deappreciable amount of radior frequency en-A Si, The combination in a signaling system of an electron discharge device having grid and pla-te circuits, a coupling between said circuits for producing radio frequency currents in said circuits and for amplifying the radio frequency currents thus produced, and

a coupling between the said circuits for transferring energy from the plate to the grid circuit at an audio frequency, and thereby amplifying the effect in the grid circuit of audio frequency current impressed thereon.

9. A system for producing alternating currents comprising an electron discharge device having grid and plate circuits which are so organized and coupled together that oscillations will be produced, the plate circuit of said device comprising two parallel branches, one of said branches including a source of unidirectional Current and an induct'ance for maintaining' an alternating potential upon the electrodes of the device, and

the second branch including a capacity andV an induct'ance which 1s coupled to an 1n-.

ductance in the grid circuit.

In witness whereof, I have hereunto set my hand' this 12th day of January 1917.

ALFRED N. GOLDSMITH. 

